Main Points. Pre-reading: Wednesday Oct 24 = Pauli and Buskirk Monday Oct 26 = Ford et al

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1 Main Points 1) The biology of migration -- convergent evolution of migratory systems -- biogeography of migratory systems -- resident and migrant strategies -- example: ideal free muskrats 2) The conservation of migrations -- human disturbance, movement barriers, and climate change -- example: cultural transmission of migratory behavior (Jesmer et al reading) -- example: shifting phenologies, predator reintroduction, and the costs and benefits of migrating Pre-reading: Wednesday Oct 24 = Pauli and Buskirk Monday Oct 26 = Ford et al Terms: partial migration, ideal free distribution, life history polymorphism, phenology 1

2 1500 km 800 km 11,000 km 2000 km 1300 km 2

3 Population growth review 3

4 Convergent evolution of migration Common attributes of migratory systems: 1) resource is sufficiently attractive to warrant moving such distances 2) return movement is initiated by the depletion of the periodic resource 800 km 2000 km 4

5 Convergent evolution of migration Common attributes of migratory systems: 1) resource is sufficiently attractive to warrant moving such distances 2) return movement is initiated by the depletion of the periodic resource 3) no physical barriers to movement 4) cycle of available resources must be 800 km predictable based on external cues 2000 km 5

6 Convergent evolution of migration Common attributes of migratory systems: 1) resource is sufficiently attractive to warrant moving such distances 2) return movement is initiated by the depletion of the periodic resource 3) no physical barriers to movement 4) cycle of available resources must be 800 km predictable based on external cues 5) movement of population is directional 2000 km 6

7 Discussion Q: what environmental variables would you expect to go hand-in-hand with migratory systems? 800 km 2000 km 7

8 The biogeography of migratory systems Seasonal resource gradients (particularly rainfall or snowmelt) typify migratory systems. Thirgood et al

9 The biogeography of migratory systems Seasonal resource gradients (particularly rainfall or snowmelt) typify migratory systems. ~30 historic migrations of 14 species in Africa (of which 6 migrations of 9 species are extant). 9

10 The biogeography of migratory systems Thirgood et al

11 Right here in your own backyard! (migrationinitiative.org) 11

12 The evolution of novelty the evolution of a ruminant stomach is thought to have resulted in the radiation of bovids (cattle, goats, sheep, antelopes) and cervids (deer) ~50-100,000 years ago 12

13 The evolution of novelty this novelty probably made it possible to migrate over long distances, and increased carrying capacities by permitting the exploitation of a previously-underutilized resource (i.e., seasonally-available forage) 13

14 Partial migration populations of most species of mammals that migrate are partially migratory, composed of a mix of migrants and residents 14

15 Partial migration in most partially migratory populations, migrants outnumber residents life history polymorphism = multiple strategies within a population, often resulting in equivalent fitness 15

16 Ideal Free Distribution IFD = a hypothesis about how animals distribute themselves among habitats to maximize individual gains (for example, energy intake) Assumptions: 1) animals are ideal (i.e., perfect) in assessing the distribution of resources among habitats or patches 16

17 Ideal Free Distribution IFD = a hypothesis about how animals distribute themselves among habitats to maximize individual gains (for example, energy intake) Assumptions: 1) animals are ideal (i.e., perfect) in assessing the distribution of resources among habitats or patches 2) animals are free to distribute themselves among habitats or patches 17

18 Ideal Free Distribution IFD = a hypothesis about how animals distribute themselves among habitats to maximize individual gains (for example, energy intake) Assumptions: 1) animals are ideal (i.e., perfect) in assessing the distribution of resources among habitats or patches 2) animals are free to distribute themselves among habitats or patches 3) first arrivals get first dibs 18

19 Ideal Free Muskrats per capita calories # muskrats in habitat 19

20 Ideal Free Muskrats per capita calories Habitat 1 = cattail marsh # muskrats in habitat 20

21 Ideal Free Muskrats per capita calories Habitat 2 = open lake Habitat 1 = cattail marsh # muskrats in habitat 21

22 Ideal Free Muskrats per capita calories Habitat 2 = open lake Habitat 1 = cattail marsh # muskrats in habitat 22

23 The conservation of migrations Migrations are jeopardized when the fitness costs of migration override the benefits Factors causing the decline of migrations (and migratory species): 1) Overexploitation made possible by aggregations 23

24 The conservation of migrations Factors causing the decline of migrations (and migratory species): 2) Barriers and/or bottlenecks to migration 24

25 Migrationinitiative.org. 25

26 The conservation of migrations cultural transmission = transmission of information from generation to generation, through which knowledge can be inherited. = bighorn sheep = moose Jesmer et al

27 The conservation of migrations Factors causing the decline of migrations (and migratory species): 3) Shifting phenologies reduce the profitability of migration Middleton et al

28 The conservation of migrations Factors causing the decline of migrations (and migratory species): 3) Shifting phenologies reduce the profitability of migration Middleton et al

29 Declines in migratory, but not resident elk in the GYE migratory resident 29

30 Declines in migratory, but not resident elk in the GYE Shifting phenology (the timing of plant growth) resulted in reduced food quality for migratory elk as time progressed. This coincided with warmer, drier springs. 30

31 Declines in migratory, but not resident elk in the GYE Shifting phenology (the timing of plant growth) resulted in reduced food quality for migratory elk as time progressed. This coincided with warmer, drier springs. 31

32 Declines in migratory, but not resident elk in the GYE Reintroduction of wolves and increased numbers of grizzly bears coincided with elk declines. Middleton et al